Out-of-bounds Read in OpenBSD
CVE-2026-56099
OpenBSD before commit 6a23123 (2026-06-18) contains an out-of-bounds read vulnerability in the mpls_do_error function within sys/netmpls/mpls_input.c that allows remote attackers to disclose kernel stack memory by sending crafted MPLS frames with 16 labels and no Bottom-of-Stack bit set.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
EPSS exploit prediction
EPSS: 0.005 (40.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- OpenBSD
- OpenBSD Src — versions 0
Weakness classification (CWE)
References
- pop.argus-systems.ai/advisory/adv-040.html (Exploit, technical-description, Patch, Third Party Advisory, exploit)
- github.com/openbsd/src/commit/6a23123ec05f1eb29cfcaae0f3a468b2e1983cfd (Patch, patch)
- www.vulncheck.com/advisories/openbsd-mpls-do-error-kernel-stack-memory-disclosu… (Third Party Advisory, third-party-advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Patch, Mailing List, Third Party Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Exploit, Patch, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2026-56099?
- CVE-2026-56099 is a medium-severity vulnerability in OpenBSD, classified under Out-of-bounds Read. CVSS score: 5.3/10. Published 2026-06-18.
- How severe is CVE-2026-56099?
- Medium severity. CVSS v3 base score is 5.3 out of 10.